STAT – Multi-character process state. See section PROCESS STATE CODES for the different values meaning.

PROCESS STATE CODES
Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process:
D uninterruptible sleep (usually IO)
R running or runnable (on run queue)
S interruptible sleep (waiting for an event to complete)
T stopped, either by a job control signal or because it is being traced
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z defunct ("zombie") process, terminated but not reaped by its parent
For BSD formats and when the stat keyword is used, additional characters may be displayed:
< high-priority (not nice to other users)
N low-priority (nice to other users)
L has pages locked into memory (for real-time and custom IO)
s is a session leader
l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+ is in the foreground process group

START – Time the command started.

TIME – Accumulated cpu time, user + system. The display format is usually “MMM:SS”, but can be shifted to the right if the process used more than 999 minutes of cpu time.

COMMAND – Command with all its arguments as a string. The output in this column may contain spaces. A process marked <defunct> is partly dead, waiting to be fully destroyed by its parent.

Because we used the f flag, in the COMMAND column we can see a tree like structure that tells us about parent-child inter-process relationships. For example, in the output above, we can see that the konsole process started a /bin/bash process. Therefore, the konsole process is the parent and the /bin/bash process is the child of konsole.

In the example above, we ran ps aux -e -T and an extra column was added: SPID, which is a light weight process (thread) ID. In the output above we have the qtcreator application that started 8 threads. The qtcreator is a process that has the PID of 15534 and each of it’s 8 threads has it’s own thread identifier(SPID).

proc filesystem

If your operating system supports the proc filesystem, you can see more details about each process in /proc/PID like this: